We are proposing to extend our studies on cellular growth in normal, malnourished and recovering animals with the objective of uncovering some of the mechanisms involved in producing the changes we and others have previously described. Specifically we are investigating RNA metabolism in liver and brain during normal growth and the effect of malnutrition and recovery on RNA metabolism. We have completed a number of studies of RNA degradation and have demonstrated that malnutrition increases the rate of degradation and elevates the activity of alkaline (pH 7.8)RNase. We plan to continue these studies to examine the changes which occur with recovery. In addition we are proposing to initiate studies of ribosomal RNA synthesis and maturation and polyamine metabolism in liver and brain during normal growth and in malnourished and recovering animals. We are presently able to separate nucleoli, nucleoplasm and cytoplasm and to quantitate various species of rRNA from each of these fractions using gel electrophoresis. We have also set up methodology for determining polyamines (putrescine, spermidine and spermine) and for measuring the major enzymes involved in the synthesis of polyamines. Finally, we are proposing to extend our observations on the usefulness of RNase activity in placenta, serum and urine as a clinical "marker" of prenatal and postnatal nutritional status and to explore the possibility that polyamine concentration in these fluids and tissues may be similarly useful. BIBLIOGRAPHIC REFERENCES: Winick, M. and Rosso, P.: Brain DNA synthesis in protein-calorie malnutrition. In: Protein-Calorie Malnutrition. Ed., Olson, R.E. New York, Academic Press, 1975, p. 93. Winick, M.: Maternal nutrition and intrauterine growth failure. In: Modern Problems in Pediatrics, Vol. 14. Ed. Canosa, C.A. Basel, S. Karger, 1975, p. 48.